1. Field of the Invention
The present invention relates to a dispenser for a liquid crystal display panel and a method for detecting a residual quantity of a dispensing material using the dispenser, and more particularly, to a dispenser for a liquid crystal display panel and a method for detecting a residual quantity of a dispensing material using the dispenser that are capable of accurately detecting a residual quantity of a dispensing material and removing a defect occurrence factor of a liquid crystal display panel.
2. Discussion of the Related Art
In general, a liquid crystal display is a display device where data signals that correspond to picture information are individually supplied to liquid crystal cells arranged in a matrix form. The light transmittance of each of the liquid crystal cells is controlled to display a desired picture. The liquid crystal display device includes a liquid crystal display panel having liquid crystal cells arranged in a matrix form and a driver integrated circuit (IC) for driving the liquid crystal cells. The liquid crystal display panel also has a color filter substrate and a thin film transistor array substrate that face each other with a liquid crystal layer positioned between the color filter substrate and the thin film transistor array substrate.
Data lines and gate lines are formed on the thin film transistor array substrate of the liquid crystal display panel. These lines cross at right angles to thereby define liquid crystal cells adjacent to each of the crossings. The data lines transmit a data signal supplied from the data driver integrated circuit to the liquid crystal cells. The gate lines transmit a scan signal supplied from the gate driver integrated circuit to the liquid crystal cells. The gate driver integrated circuit sequentially supplies scan signals to the gate lines so that the liquid crystal cells arranged in the matrix form can be sequentially selected line by line. A data signal is supplied to the selected one line of liquid crystal cells from the data driver integrated circuit.
A common electrode and a pixel electrode are respectively formed on the inner side of the color filter substrate and the thin film transistor array substrate. An electric field is applied across the liquid crystal layer via a common electrode and a pixel electrode. More specifically, a pixel electrode is formed in each liquid crystal cell on the thin film transistor array substrate. The common electrode is integrally formed across the entire surface of the color filter substrate. Therefore, by controlling a voltage applied to the pixel electrode when a voltage is applied to the common electrode, light transmittance of the liquid crystal cells can be individually controlled. To control the voltage applied to the pixel electrode by liquid crystal cells, a thin film transistor used as a switching device is formed in each liquid crystal cell. Elements of the liquid crystal display device will now be described.
FIG. 1 is a plan view of the unit liquid crystal display panel formed by a thin film transistor array substrate and a color filter substrate according to the related art. As shown in FIG. 1, the liquid crystal display panel 100 includes an image display part 113 where the liquid crystal cells are arranged in a matrix form, a gate pad part 114 connected to the gate lines of the image display part 113, and a data pad part 115 connected to the data lines. The gate pad part 114 and the data pad part 115 are formed along an edge region of the thin film transistor array substrate 101 that does not overlap with the color filter substrate 102. The gate pad part 114 supplies a scan signal from the gate driver integrated circuit to the gate lines of the image display part 113, and the data pad part 115 supplies image information from the data driver integrated circuit to the data lines of the image display part 113.
Data lines to which image information is applied and gate lines to which a scan signal is applied are provided on the thin film transistor array substrate 101. The data lines and the gate lines intersect each other. Additionally, a thin film transistor for switching the liquid crystal cells is provided at each intersection of the data lines and the gate lines. A pixel electrode for driving the liquid crystal cells connected to the thin film transistor is provided on the thin film transistor array substrate 101, and a passivation film protecting the pixel electrode and the thin film transistor is formed on the entire surface of the thin film transistor array substrate 101.
Color filters in the cell regions are separated by the black matrix. A common transparent electrode is provided on the color filter substrate 102. A cell gap is formed by a spacer between the thin film transistor array substrate 101 and the color filter substrate 102, which are attached to each other by a seal pattern 116 formed along an outer edge of the image display part 113.
In fabricating the liquid crystal display panel, a method for simultaneously forming a multiple liquid crystal display panels on a large-scale mother substrate is typically used. Thus, this method requires a process for separating the liquid crystal display panels from the large-scale mother substrate by cutting and processing the mother substrate having the plurality of liquid crystal display panels formed thereon. After a liquid crystal display panel is separated from the large-scale mother substrate, liquid crystal is injected through a liquid crystal injection opening to form a liquid crystal layer in the cell-gap which separates the thin film transistor array substrate 101 and the color filter substrate 102, and then the liquid crystal injection opening is sealed.
To fabricate a liquid crystal display panel, the following processes are generally required. First, the thin film transistor array substrate 101 and the color filter substrate 102 are separately fabricated on first and second mother substrates. The first and second mother substrates are attached in such a manner that a uniform cell-gap is maintained therebetween. The attached first and second mother substrates are cut into unit panels. Then, liquid crystal is injected to the cell-gap between the thin film transistor array substrate 101 and the color filter substrate 102. A process of forming the seal pattern 116 along an outer edge of the image display part 113 is required to attach the thin film transistor array substrate 101 and the color filter substrate 102. The related art seal pattern forming method will now be described.
FIGS. 2A and 2B illustrate a screen printing method to form a seal pattern. As shown in FIGS. 2A and 2B, there are provided a screen mask 206 patterned so that a seal pattern forming region is selectively exposed. Then, a rubber squeegee 208 for selectively supplying a sealant 203 to the substrate 200 through the screen mask 206 is used to form the seal pattern 216. Thus, the seal pattern 216 is formed along an outer edge of the image display part 213 of the substrate 200 and a liquid crystal injection opening is formed at one side. The opening is for injecting liquid crystal into a gap between the thin film transistor array substrate 101 and the color filter substrate 102. The seal pattern 216 prevents the leakage of the liquid crystal. In general, the screen printing method includes: applying the sealant 203 on the screen mask 206 having a seal pattern forming region patterned thereon, and forming the seal pattern 216 on the substrate 200 through printing with the rubber squeegee 208; and drying the seal pattern 216 by evaporating a solvent contained in the seal pattern 216 and leveling it.
The screen printing method is widely used because it has the advantage of processing ease. However, it has the disadvantage of sealant waste. More particularly, sealant is wasted because sealant is applied to the entire surface of the screen mask and then the seal pattern is printed with the rubber squeegee such that the excess sealant material, which is not printed, is thrown away. In addition, the screen printing method has another disadvantage in that a rubbed orientation film (not shown) formed on the substrate 200 is degraded as a result of the screen mask 206 being brought into contact with the substrate 200. The degradation of the rubbed orientation film degrades picture quality of the liquid crystal display device. Therefore, to overcome the shortcomings of the screen printing method, a seal dispensing method has been proposed.
FIG. 3 is an exemplary view of a dispensing method for forming a seal pattern in accordance with the related art. As shown in FIG. 3, while a table 310 with the substrate 300 loaded thereon is being moved in the forward/backward and left/right directions. A seal pattern 316 is formed along an outer edge of the image display part 313 of the substrate 300 by applying a certain pressure to sealant in the syringe 301. In this seal dispensing method, since the sealant is selectively supplied to the region where the seal pattern 316 is to be formed, sealant consumption can be reduced. In addition, since the syringe is not in contact with the orientation film (not shown) of the image display part 313 of the substrate 300, the rubbed orientation film can not be damaged and thus the picture quality of the liquid crystal display device is not degraded.
In the case of forming the seal pattern 316 on the substrate 300 loaded on the table 310 by using the syringe 301, a technique is required to detect precisely the residual quantity of sealant that remains in the syringe 301. That is, if the sealant filled in the syringe 301 is used up, the seal pattern 316 may not be completely formed on the substrate 300, or in a worse case, the seal pattern 316 is not even formed on the substrate 300, generating a defective liquid crystal display panel. Therefore, an operator should be notified when a residual quantity of the sealant remaining in the syringe 301 is not sufficient such that the syringe 301 can be replaced with a different syringe 301 filled with sealant before the residual quantity reaches such a minimum quantity that will not form a proper seal pattern 316.
In the related art, the operator detects an initial charge quantity of the sealant filled in the syringe 301 and calculates a consumed quantity of the sealant by calculating a length of the seal pattern 316 during its formation to thereby estimate a residual quantity of the sealant remaining in the syringe 301. However, the related art of a method for detecting a residual quantity of sealant based on the arithmetic distance calculation has a problem in that operators make errors in detecting or noting the initial charge quantity. In addition, the residual quantity of sealant estimated by the arithmetic length calculation may differ from an actual residual quantity of sealant remaining in the syringe 301. That is, even through the seal pattern 316 is formed with the same length on the substrate 300, the consumed quantity of sealant may differ depending on a width and a height of the seal pattern 316, resulting in the residual quantity of sealant determined by the arithmetic length calculation being different from an actual residual quantity of sealant remaining in the syringe 301. Thus, even if the syringe 301 has enough sealant, it may be replaced with another syringe 301 filled with sealant, which wastes sealant and thus increases material expense. Conversely, even though the syringe 301 does not have enough sealant, the syringe 301 may still be used to form the seal pattern 316. Then, the seal pattern 316 may be partially formed, or in a worse case, no seal pattern is formed causing a defective liquid crystal display panel and degradation of a productivity.